and to find how many seconds that is:1199.647*24 because 24 hours, then times 60 because 60 minutes in an hour, then times another 60 because 60 seconds in a minute, and we get about 1.03*10^8 seconds.

average velocity to calculate the forceFor acceleration, (v2-v1)/(t2-t1)(19.88km/s-0km/s)/(1.03*10^8s-0s)= approximately 1.93^-7km/s/s

Then we multiply that by the mass to see how much force it carries if left fully intact

2.5*10^16kg * 1.93*10^-7km/s/s = approximately 4.82*10^9N of force.

The number of meteoroids in a meteor shower various greatly, but seem to often fall in the realm of 15-50 pieces per hour, although most of the things in a meteor shower are pieces of dust.http://meteorshowers...or_showers.html

Using Newtons does not make for a good conversion with dimensional analysis, so I will calculate it'sapproximate kinetic energy instead.

E(sub k) = 1/2mv^2

Kinetic energy = (1/2)(2.5*10^16kg)(19.88m/s)^2=4.94*10^18J

1 joule of kinetic energy approximately equals 1 joule of thermal energy.If all asteroid's energy was converted to thermal energy, it would releaseapproximately 4.94*10^18 joules of thermal energy.

2.5*10^16kg

Using the Specific heat of Earth's atmosphere to calculate the temperature change

Then I divide the left side by everything on the right side except by T, and dividing is the same as multiplying by 1 over that number

(4.94*10^15kJ/1)(1/5.3*10^(18)kg)(1kgK/1.01kJ) = the units cancel out and I am left with a temperature change of .0009228 Kelvin

And in case I forgot to multiply something by 1000 like I did with newtons, I will multiply the amount of joules the asteroid has by 1000 to play it safe

(4.94*10^18kJ/1)(1/5.3*10^(18)kg)(1kgK/1.01kJ) = the units cancel out and I am left with a temperature change of .9228... Kelvin

If my original theory and it's proof is correct, if the asteroid 951 Gaspara which is 6.1km large was heading for Earth and we fragmented it into pieces so small that all of it's kinetic energy would be converted to thermal energy via friction causing the heating and then vaporization of the fragments before they reached the ground, Earth would be saved and there would be a temperature change less than 1 Kelvin.

Based on this I think that it is safe to assume an asteroid 10km large would raise Earth's temperature a little over 1 K or a little over 1 hundredth of a K,and an asteroid 20km large would definitely raise Earth's atmosphere's temperature by a little over 2 K or .002 K.

I looked about the conversion for Kelvin to Celsius and it appears 1K approximately = -272.15 degrees Celsius.

and to find how many seconds that is:1199.647*24 because 24 hours, then times 60 because 60 minutes in an hour, then times another 60 because 60 seconds in a minute, and we get about 1.03*10^8 seconds.

average velocity to calculate the forceFor acceleration, (v2-v1)/(t2-t1)(19.88km/s-0km/s)/(1.03*10^8s-0s)= approximately 1.93^-7km/s/s

Then we multiply that by the mass to see how much force it carries if left fully intact

2.5*10^16kg * 1.93*10^-7km/s/s = approximately 4.82*10^9N of force.

Yeah, here we have the same bad nonsense calculation again, exactly as it was posted before, it even contains the same math error.

It's the wrong way to do it and since it's not even done correctly it contains a false result too.

The number of meteoroids in a meteor shower various greatly, but seem to often fall in the realm of 15-50 pieces per hour, although most of the things in a meteor shower are pieces of dust.http://meteorshowers...or_showers.html

But we are not talking about a meteor shower here, we are discussing the fragmentation of one asteroid where all pieces will hit Earth in one swarm.

From the asteroid's point of view the Earth is a circular target with a diameter of about 12 742 km and a moving speed of around 29.78 km/s, that means that for all the pieces to hit Earth they must all fall within 12742/29.78=428 seconds or about 7 minutes, otherwise some parts will miss Earth.

BTW: your link is not working.

Using Newtons does not make for a good conversion with dimensional analysis, so I will calculate it'sapproximate kinetic energy instead.

E(sub k) = 1/2mv^2

Kinetic energy = (1/2)(2.5*10^16kg)(19.88m/s)^2=4.94*10^18J

It is good to see that you finally are applying the correct formula for kinetic energy that I provided to you.

But we argued about an impact speed similar to that of Comet Shoemaker-Levy 9 that hit Jupiter with a collision speed of approximately 60 km/s.

I am a reasonable man so if you can provide a valid motivation to change the impact speed to another sensible value I can accept that.

However until then, I will consider the rest of your post as an lousy attempt to change the goalpost and fudge the numbers in your favor.

Forgot??? How could you forget such a great place like this? But don't worry, we don't have time restrictions on replies here.

Umm, if you realize you got that wrong then why repeat the exact same mistake again? Didn't you read and understand my last post?

If you think that posting this long list of unnecessarily data makes your post look more legitimate, you are wrong.

Furthermore it is against the Rules to duplicate others work without clearly quoting and linking to the source.

Yeah, here we have the same bad nonsense calculation again, exactly as it was posted before, it even contains the same math error.

It's the wrong way to do it and since it's not even done correctly it contains a false result too.

But we are not talking about a meteor shower here, we are discussing the fragmentation of one asteroid where all pieces will hit Earth in one swarm.

From the asteroid's point of view the Earth is a circular target with a diameter of about 12 742 km and a moving speed of around 29.78 km/s, that means that for all the pieces to hit Earth they must all fall within 12742/29.78=428 seconds or about 7 minutes, otherwise some parts will miss Earth.

BTW: your link is not working.

It is good to see that you finally are applying the correct formula for kinetic energy that I provided to you.

But we argued about an impact speed similar to that of Comet Shoemaker-Levy 9 that hit Jupiter with a collision speed of approximately 60 km/s.

I am a reasonable man so if you can provide a valid motivation to change the impact speed to another sensible value I can accept that.

However until then, I will consider the rest of your post as an lousy attempt to change the goalpost and fudge the numbers in your favor.

Dude, I proved my theory right which doesn't even normally happen on these forums, your just arguing semantics and details because you don't want to admit you were wrong to automatically say humanity would be destroyed with my theory in place or there's some very very large potions of my posts your not understanding.http://en.wikipedia....wiki/951_Gaspra

It says right there on the side the average orbital speed is about 20km/s which is most likely the speed it would hit Earth at.and it has all the other stuff like about the mass, I got my info from wikipedia, I mostly just copied and pasted an extended link which is why there's useless data in there.Maybe the Earth could be moving towards or away the asteroid, but it could also easily be an impact into the side of Earth and thus it wouldn't really matter. If all of 951 Gaspara's kinetic energy was converted to thermal energy in it's current state, it definitely wouldn't raise Earth's atmosphere's temperature by more than 2 Kelvin. I even multiplied Gaspara's energy by 1000 unnecessarily just incase I did make the same mistake like you said I had and it's still less than 1 Kelvin.Actually, the word "impact" is a sever over-exaggeration because I'm talking about millions of small fragments, the asteroid wouldn't hit Earth at all, the pieces would burn up in the atmosphere practically harmlessly.

Also, I copied the Newtons thing to show where I had left off from, and I clearly stated I was going to use kinetic energy instead of Newtons for my calculations from that point on.Some asteroids are faster, some are slower, but the temperature change will be around .0001-3 Kelvin with many of those relatively similar sized asteroids in our solar system since there are varying speeds.

What specifically do you even think needs to be multiplied by 1000 in my new calculations? Because I don't see a reason to in addition to the calculations I already did. Just because a unit is squared doesn't mean the coefficient is.

If I say 1X * 5X, I don't say (1 * 5)^2 * X^2, I say 5X^2. (1*5)^2 would equal 25, and 1x times 5x does not equal 25x^2, it equals 5x^2.

and the only other reason I could think of for you thinking I need to multiply something by 1000 is conversion from a unit to kilo-units.1 joule does not = 1000 kilo joules, because there are 1000 joules in one kilo-joule. 1 joule is 1 1/1000 if a kilo-joule, thus I divide joules by 1000, NOT multiply by 1000, to convert that number to kilo-joules, and it also needs to work that way so the units cancel out at all (see dimensional analysis).

The comet that hit Jupiter was very large and more rare anyway, it left a scars the size of Earth itself.

Not only that but the system of Earth would want to return to an equilibrium anyway as Earth loses much heat energy to space, and thus Earth would try to cool off even if I had to multiply Gaspara's energy by 10000 which would make the temperature change about 9 Kelvin.

Dude, I proved my theory right which doesn't even normally happen on these forums, your just arguing semantics and details because you don't want to admit you were wrong to automatically say humanity would be destroyed with my theory in place or there's some very very large potions of my posts your not understanding.

While it's generally considered good to have self esteem, one should take great care to not be too confident and overestimate one's capabilities.(Especially when you are continuously repeating the same mistake that has been pointed out to you several times already.)

It says right there on the side the average orbital speed is about 20km/s which is most likely the speed it would hit Earth at.and it has all the other stuff like about the mass, I got my info from wikipedia, I mostly just copied and pasted an extended link which is why there's useless data in there.Maybe the Earth could be moving towards or away the asteroid, but it could also easily be an impact into the side of Earth and thus it wouldn't really matter. If all of 951 Gaspara's kinetic energy was converted to thermal energy in it's current state, it definitely wouldn't raise Earth's atmosphere's temperature by more than 2 Kelvin. I even multiplied Gaspara's energy by 1000 unnecessarily just incase I did make the same mistake like you said I had and it's still less than 1 Kelvin.Actually, the word "impact" is a sever over-exaggeration because I'm talking about millions of small fragments, the asteroid wouldn't hit Earth at all, the pieces would burn up in the atmosphere practically harmlessly.

First I must say that I find it rather petty and unsportsmanlike for you to quibble on the impact speed which is only a factor of 3 times when you claim to be willing to multiply with an factor of 1000 times "just in case". 60 km/s was the speed I mentioned already back in post #10 and what you have been arguing against since then, you did not mention any speed limits in your claim in the OP or before this post.

Secondly, Gaspra's orbital speed is certainly not the most likely speed it will hit Earth with, it is the speed it moves around the Sun with and not a speed relative Earth in Earth's orbit. In Gaspra's current orbit it will never hit Earth or cross paths with Earth's orbit. For it to move closer to Earth inwards in the solar system its orbit will have to change and then it will certainly speed up when accelerated towards the Sun. But IF we make a hypothetical example and assume that it or a similar asteroid will hit Earth then we are free to assume any reasonable speed we want.

Even while changing the speed seem unfair to me, I will still let you have your speed of 20 km/s, because it's inside a reasonable speed range.

What specifically do you even think needs to be multiplied by 1000 in my new calculations? Because I don't see a reason to in addition to the calculations I already did. Just because a unit is squared doesn't mean the coefficient is.

While it's generally considered good to have self esteem, one should take great care to not be too confident and overestimate one's capabilities.(Especially when you are continuously repeating the same mistake that has been pointed out to you several times already.)

First I must say that I find it rather petty and unsportsmanlike for you to quibble on the impact speed which is only a factor of 3 times when you claim to be willing to multiply with an factor of 1000 times "just in case". 60 km/s was the speed I mentioned already back in post #10 and what you have been arguing against since then, you did not mention any speed limits in your claim in the OP or before this post.

Secondly, Gaspra's orbital speed is certainly not the most likely speed it will hit Earth with, it is the speed it moves around the Sun with and not a speed relative Earth in Earth's orbit. In Gaspra's current orbit it will never hit Earth or cross paths with Earth's orbit. For it to move closer to Earth inwards in the solar system its orbit will have to change and then it will certainly speed up when accelerated towards the Sun. But IF we make a hypothetical example and assume that it or a similar asteroid will hit Earth then we are free to assume any reasonable speed we want.

I don't think applying the Heat equation like this is correct, but all I have to do is show that your current estimate is wrong so:

Since Kelvin and Celsius have equal scale and the average air temperature at Earth's surface is around 15°C it would rise to almost 950 °Celsius.

Unless you don't consider breathing air hot enough to melt aluminium to be a problem, I think your evidence just went up in smoke.

That would be a good thing but not what we are arguing about, I am the one proposing deflection and you are proposing destruction, remember?

If some parts of the asteroid miss Earth then it's not the fragmentation itself that saves Earth but the deflection of those parts.

Alright, I redid the math from scratch and it seems to match yours, so I'll agree with you for now and retract the statement and that converting all of an asteroid's kinetic energy to thermal energy via friction with Earth's atmosphere isn't the best option. I'm still going to get it looked over by an actual physicist though just to make sure.

That said, half and half probably wouldn't be much better either, which leaves us with 3 other options:Blow it up completelyDeflect it,Break it into pieces not small enough to transfer that much thermal energy but not large enough to actually cause damage, for which the only result would really be a vector map, the energy is still conserved, but all it would do in that form is simply push Earth or change its orbit a little bit or something and probably destroy some homes and knock down some trees. I suppose I could calculate the average volume and mass of each piece and see how much energy they carry depending on how many pieces its broken into, but then I'd also have ton consider the critical size for when it gets too small so that all of its energy would be converted to thermal energy, leading us back to the first problem. I looked into canceling out its energy, the highest energy nuclear device ever detonated, castle/bravo, only released 63,000 TJ, it it took something like over 700000 of them to equal the kinetic energy of the of meteor assuming the meteor calculations are correct.

Maybe you can help with the "deflecting" thing since that's your theory. Maybe if it's speed is super fast, but it would have to be way way faster than the meteor to deliver enough energy to move 2.5*10^16kg of matter out of the way and there would need to be some way to push it at the right angle.

If anyone else has any theories free to jump in too, this is just a speculation topic.

That said, half and half probably wouldn't be much better either, which leaves us with 3 other options:Blow it up completelyDeflect it,Break it into pieces not small enough to transfer that much thermal energy but not large enough to actually cause damage, for which the only result would really be a vector map, the energy is still conserved, but all it would do in that form is simply push Earth or change its orbit a little bit or something and probably destroy some homes and knock down some trees. I suppose I could calculate the average volume and mass of each piece and see how much energy they carry depending on how many pieces its broken into, but then I'd also have ton consider the critical size for when it gets too small so that all of its energy would be converted to thermal energy, leading us back to the first problem.

If we "Break it into pieces" and none of them bounces off Earth then we have a perfectly inelastic collision where conservation of momentum applies.

m is mass of bodyu is initial velocityv is final velocity

However a very large portion of the kinetic energy will still get turned into thermal energy when the bodies gets deformed in the collisions.

Maybe you can help with the "deflecting" thing since that's your theory. Maybe if it's speed is super fast, but it would have to be way way faster than the meteor to deliver enough energy to move 2.5*10^16kg of matter out of the way and there would need to be some way to push it at the right angle.

I don't have a "deflecting" theory, but IF we manage to deflect it, then it obviously won't hit Earth and we are saved.

There are several ideas proposed in the link I posted in post #4 and the main aspect is that an early change doesn't have to be so large.

However a very large portion of the kinetic energy will still get turned into thermal energy when the bodies gets deformed in the collisions.

I know, but theoretically there should be a size of the meteor where they to release thermal energy, but they are not small enough to release too much thermal energy but not large enough to cause major damage to the ground.

I don't have a "deflecting" theory, but IF we manage to deflect it, then it obviously won't hit Earth and we are saved.

Right, but, how realistic is it to throw a 2 ton piece of metal and deflect 2.5*10^16 kilograms of matter?

Ion beams? Mass drivers? I guess, seems kind of complex, though it does say in that very link that there is a potential to let pieces burn up in the atmosphere, even if there potentially exists the same problem. Thought I suppose, Earth won't stay at 920 Kelvin, and it wouldn't happen all at once. Maybe if it could be spread out enough for Earth to return to equilibrium before the next swarm, but doing that might be too complex.Actually, the calculations on this thread might even be the citation needed for that paragraph.

The only one where there doesn't seem to be any direct setbacks is I guess trying to blow it up completely, based on that link, but perhaps studies should be done on the far side of the moon where nuclear devices are detonated and there are orbiting satellites to scan how the radiation spreads out.

I know, but theoretically there should be a size of the meteor where they to release thermal energy, but they are not small enough to release too much thermal energy but not large enough to cause major damage to the ground.

No, if the kinetic energy is not released by heating the atmosphere, then it will be released violently at impact with the ground.

It is about 1,200 m (4,000 ft) in diameter, some 170 m deep (570 ft), and is surrounded by a rim that rises 45 m (150 ft) above the surrounding plains.

(...)

The object that excavated the crater was a nickel-iron meteorite about 50 meters (54 yards) across, which struck the plain at a speed of several kilometers per second. Impact energy has been estimated at about 10 megatons. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at a speed of up to 20 kilometers per second (45,000 mph), but more recent research suggests the impact was substantially slower, at 12.8 kilometers per second (28,600 mph). It is believed that about half of the impactor's bulk was vaporized during its descent, before it hit the ground.

It is about 1,200 m (4,000 ft) in diameter, some 170 m deep (570 ft), and is surrounded by a rim that rises 45 m (150 ft) above the surrounding plains.

(...)

The object that excavated the crater was a nickel-iron meteorite about 50 meters (54 yards) across, which struck the plain at a speed of several kilometers per second. Impact energy has been estimated at about 10 megatons. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at a speed of up to 20 kilometers per second (45,000 mph), but more recent research suggests the impact was substantially slower, at 12.8 kilometers per second (28,600 mph). It is believed that about half of the impactor's bulk was vaporized during its descent, before it hit the ground.

That's 50 meters across though which is pretty big, I as thinking more like 1 meter across at most. Most of the meteors that burn up into the atmosphere are around the size of dust particles, maybe a few cubic centimeters sometimes too. If maybe there was some approximate number for the rate that a meteor converts kinetic energy to thermal energy via friction with the atmosphere, I could use it.

That's 50 meters across though which is pretty big, I as thinking more like 1 meter across at most. Most of the meteors that burn up into the atmosphere are around the size of dust particles, maybe a few cubic centimeters sometimes too. If maybe there was some approximate number for the rate that a meteor converts kinetic energy to thermal energy via friction with the atmosphere, I could use it.

If half of the Arizona meteorite was vaporized during its descent then half of its initial kinetic energy was released into the atmosphere.

If half of the Arizona meteorite was vaporized during its descent then half of its initial kinetic energy was released into the atmosphere.

I see, so your saying the meteor has to be quite large to not completely vaporize, but there's small meteors all over the planet that weren't a ton bigger when they entered the atmosphere or they would have been on the news. I guess maybe that one in Chile. There's also when meteors explode, which is that sometimes meteors will spontaneously explode when heated up like that.We can't say for sure that half of a meteor's energy will be thermal and the other half will be kinetic though, because some vaporize completely and others don't vaporize that much at all, we need an actual number for the rate at which a meteor vaporizes and releases thermal energy.

I see, so your saying the meteor has to be quite large to not completely vaporize, but there's small meteors all over the planet that weren't a ton bigger when they entered the atmosphere or they would have been on the news. I guess maybe that one in Chile. There's also when meteors explode, which is that sometimes meteors will spontaneously explode when heated up like that.We can't say for sure that half of a meteor's energy will be thermal and the other half will be kinetic though, because some vaporize completely and others don't vaporize that much at all, we need an actual number for the rate at which a meteor vaporizes and releases thermal energy.

No, I didn't mean that, I ment that smaller pieces will vaporize more of its body than larger pieces if the material is equal and a rocky piece will likely vaporize more of its body than a denser metallic piece would.

But my point still stands, even a very small piece of pebble size will release most of its kinetic energy violently as thermal energy during impact.

No, I didn't mean that, I ment that smaller pieces will vaporize more of its body than larger pieces if the material is equal and a rocky piece will likely vaporize more of its body than a denser metallic piece would.

But my point still stands, even a very small piece of pebble size will release most of its kinetic energy violently as thermal energy during impact.

Well how about we make them a little bigger then? We can make meteorites a decent size without them actually making giant craters. The speed of the asteroid would likely be slowed down by earlier failed attempts too.

i would place a nuclear weapon on it so would be in a crater and detonate it and hope that a significant amount of the detonation energy would be transferred into kinetic energy and be transferred into the object at a right angle to the trajectory
like in stargateSG1.

Edited by dragonstar57, 20 April 2012 - 01:02 AM.

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please feel free to point out my grammatical errors. I would rather have them pointed out and be able to perhaps learn from them than continue make the same mistake.

It is not closed-minded to reject claims that make no sense. If you can’t accept the possibility that an idea might be false, then you are the closed minded one. An open minded person will critically examine all claims but will not accept them if there is no reason to believe they are true or if there is reason to believe they are false.

however one must realize that every thing starts in a default belief and requires a burden of proof for the default belief to be abandoned. it would not make sense for believing in positive statements' validity so the only remaining is to not believe a positive statement until proof evidence is presented.

i would place a nuclear weapon on it so would be in a crater and detonate it and hope that a significant amount of the detonation energy would be transferred into kinetic energy and be transferred into the object at a right angle to the trajectorylike in stargateSG1.

Yeah, nukes on the meteor itself seem like it would be a good idea, I didn't know we had the technology to land on a meteor and plant a nuke, so I'd always imagined there would be some kind of missile that was just designed to detonate based on proximity, since it's a pretty hard shot to make, but there should be testing to make sure releasing enough energy to destroy and/or very quickly deflect of mass doesn't destroy a large portion of the oozone or really damage Earth that much at all.

Yeah, nukes on the meteor itself seem like it would be a good idea, I didn't know we had the technology to land on a meteor and plant a nuke, so I'd always imagined there would be some kind of missile that was just designed to detonate based on proximity, since it's a pretty hard shot to make, but there should be testing to make sure releasing enough energy to destroy and/or very quickly deflect of mass doesn't destroy a large portion of the oozone or really damage Earth that much at all.

unless we intercept it at a significant distance we are doomed.haven't seen any plans that would work if it was at close range

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please feel free to point out my grammatical errors. I would rather have them pointed out and be able to perhaps learn from them than continue make the same mistake.

It is not closed-minded to reject claims that make no sense. If you can’t accept the possibility that an idea might be false, then you are the closed minded one. An open minded person will critically examine all claims but will not accept them if there is no reason to believe they are true or if there is reason to believe they are false.

however one must realize that every thing starts in a default belief and requires a burden of proof for the default belief to be abandoned. it would not make sense for believing in positive statements' validity so the only remaining is to not believe a positive statement until proof evidence is presented.

Well how about we make them a little bigger then? We can make meteorites a decent size without them actually making giant craters. The speed of the asteroid would likely be slowed down by earlier failed attempts too.

You are not addressing my main argument, what difference would it make if the kinetic energy is released thermally by vaporization high up in the atmosphere or thermally down at the surface in the impact when the bodies gets deformed by the collisions?

It is the same total energy, even if the size is small as a pebble where it wont make any giant crater, it will still convert its kinetic energy.

Yeah, nukes on the meteor itself seem like it would be a good idea, I didn't know we had the technology to land on a meteor and plant a nuke, so I'd always imagined there would be some kind of missile that was just designed to detonate based on proximity, since it's a pretty hard shot to make, but there should be testing to make sure releasing enough energy to destroy and/or very quickly deflect of mass doesn't destroy a large portion of the oozone or really damage Earth that much at all.

at a large range a small change in the path would compound as it traveled. if the explosion just changes the trajectory by a tenth of a degree that might be enough to turn a direct hit into a near miss and saving the earth from the impact.you seem to be thinking about it as if it would be the explosives equivalent of hitting a baseball with a bat and having it sour off into spacethe outfield .it would be more like a course correction for a satellite than a batting in a baseball game just need to accelerate it a little at a right angle to its path and it will miss to one side or the other.

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please feel free to point out my grammatical errors. I would rather have them pointed out and be able to perhaps learn from them than continue make the same mistake.

It is not closed-minded to reject claims that make no sense. If you can’t accept the possibility that an idea might be false, then you are the closed minded one. An open minded person will critically examine all claims but will not accept them if there is no reason to believe they are true or if there is reason to believe they are false.

however one must realize that every thing starts in a default belief and requires a burden of proof for the default belief to be abandoned. it would not make sense for believing in positive statements' validity so the only remaining is to not believe a positive statement until proof evidence is presented.

ok i'm going to make an assumption and assume that the asteroid has a high iron concentration.
what if we shot it with a series of high speed magnetized projectiles? each one would hit it and would decrease the speed of the object.

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please feel free to point out my grammatical errors. I would rather have them pointed out and be able to perhaps learn from them than continue make the same mistake.

It is not closed-minded to reject claims that make no sense. If you can’t accept the possibility that an idea might be false, then you are the closed minded one. An open minded person will critically examine all claims but will not accept them if there is no reason to believe they are true or if there is reason to believe they are false.

however one must realize that every thing starts in a default belief and requires a burden of proof for the default belief to be abandoned. it would not make sense for believing in positive statements' validity so the only remaining is to not believe a positive statement until proof evidence is presented.